Charles-Rene, commonly known by the name of Father Reyneau, a celebrated mathematician of France, was born in the year 1656, at Brillac in the province of Anjou. When 20 years of age, he connected himself with the Oratorians, a sort of religious order, the members of which lived in community without binding themselves to the observance of any vows, and turned their chief attention to the instruction of youth. He afterwards taught philosophy at Pezenas, and next at Toulon, which requiring some degree of geometrical knowledge, he became extremely fond of that science, and cultivated and improved it to a great extent. He was, in consequence of his knowledge, invited to fill the mathematical chair at Angers in 1683, and he was also elected a member of the academy, in 1694. He undertook to reduce into a body, for the benefit of his pupils, the chief theories which were scattered through the works of Newton, Des Cartes, Leibnitz, Bernoulli, the Leipfie Acts, the Memoirs of the Paris Academy, and several other works, to which he gave the name of Analyse Demonstrée, or Analyse Demonstrated, which was published in 1708, in 2 vols. 4to.

He gave to this work the name of Analyse Demonstrated, because he therein demonstrates various methods which had not been demonstrated by their authors, or at least not with sufficient accuracy and perspicuity. This work of Reyneau was very much applauded, and it became a general maxim in France, that to follow him was the best, if not the only way, to make any extraordinary progress in the study of mathematics.

Such was his ambition to be useful, that in 1714 he published his Science du Calcul des Grandeurz, intended for the benefit of such as were wholly unacquainted with the science of geometry. Of this work a very able judge was pleased to observe, that "though several books had already appeared upon the same subject, such a treatise as that before him was still wanting, as in it every thing was handled in a manner sufficiently extensive, and at the same time with all possible exactness and perspicuity." Although many branches of the mathematics had been well discussed prior to his time, no good elements were to be met with, even of practical geometry.

When the Royal Academy of Sciences at Paris gave admission to other learned and eminent men, Father Reyneau was received into the number. The works already mentioned are all he ever published, or perhaps even composed, with the exception of a little piece upon logic; and materials for a second volume of his Science du Calcul were left behind him in manuscript. Towards the close of life he was too much afflicted with sickness to give much application to study; and he died in 1728, at 72 years of age. His many virtues and extensive erudition made this event much regretted by all who had the pleasure of being acquainted with him. It was regarded as an honour and a happiness by the first men in France, to number him among their friends, such as the chancellor of the kingdom and Malbranche, of the latter of whom Reyneau was a faithful and zealous disciple.